Introduction to Biochemistry module.pptx

bio chemistry

1. Chalimbana University School of Mathematics & Science Education Department of Chemistry Course Name : Biochemistry Chemistry Course Code : BCH 1100 Lecturer : Mwale James Phone : [phone] Email : [email protected]

2. Introduction to Biochemistry

3. What is biochemistry? Biochemistry is the chemistry that deals with the chemical compounds and processes occurring in organism or it is the chemical characteristics and reactions of a particular living organism or biological substance . Cells In this unit you will study the structure and function of cells. All living things are made of cells, and cells are the smallest units that can be alive. Schleidon and Schwann Schleidon and Schwann first described the cell theory in 1839. The theory describes a cell as a basic unit of life embraces the following ideas. 1. Every organism is composed of one or more cells; which form the building blocks of living organisms. 2.Cells arise only by the division of existing cells; i.e. continuity of life arises directly from the growth and division of single cells.

4. Cont ; 3.The cell is the smallest functional unit of life; i.e. smallest unit having properties of life. 4.Cells contain inherited information, which controls their activities. 5.Given suitable conditions, cells are capable of independent existence. Types of cells Life on Earth is classified into five kingdoms, and they each have their own characteristic kind of cell. However, the biggest division is between the cells of the prokaryote kingdoms ( monera and protista ) and those of the other three kingdoms (animals, plants and fungi), which are all eukaryotic cells.

5. Prokaryotes Usually these comprise of unicellular organisms not visible with the naked eye. The diameter ranges from 0.5-10μm. The cells divide by binary fission and no spindles are formed during the process. The DNA is circular and lies free in the cytoplasm. Very few organelles are found and are not bound by membranes . The cells are composed of small ribosomes. They have a rigid cell wall and contain polysaccharides with amino acids. They have simple flagella that lack microtubules. The sexual systems are rare, because the genetic materials pass from donor to the recipient.

6. Cont ; Although some of them are autotrophic, they do not have chloroplasts. Most of these are bacteria, blue-green algae and viruses. One generalized example of a Prokaryotic cell is shown below:

7. Cont ; Eukaryotes These are commonly multicellular and are about 10-100μm in diameter. The DNA is linear and contained in a nucleus. The DNA is associated with proteins and RNA to form chromosomes. The ribosomes are larger and may be attached to endoplasmic reticulum. They have many organelles and most of them are bound by membranes. Cell division is by mitosis, meiosis or both and it involves the formation of spindles. Cell walls are rigid and contain polysaccharides. Cellulose is the main strengthening material. They have chloroplasts containing membranes, which are usually stacked into lamellae or grana, use mitochondria for respiration.

8. Cont ; These include Plants and Animals, Protoctists and Fungi. Generalized diagrams of plant and animal cells are shown below:

9. Cell structures and functions

10. Cell Membrane (or Plasma Membrane ) This is a thin, flexible layer round the outside of all cells made of phospholipids and proteins. It separates the contents of the cell from the outside environment, and controls the entry and exit of materials.

11. Movement of substances in and out of cells We now know that plants and animals are made up of cells which have cell membrane which are selectively permeable to solutes but fully permeable to water . These solute substances include soluble food, gases like oxygen and carbon dioxide and other excretory materials. The following are the three principles that govern the movement of substances in and out of the cell; d iffusion osmosis Active transport . The two ways in which substances can enter or leave a cell are Passive and Active. Passive does not require energy while active requires energy.

12. Cont ; Under Passive we have: Simple diffusion, facilitated diffusion and osmosis ( water only) Under Active we have: Mineral salts and other solute particles

13. Cont ; Diffusion Diffusion is the net passive movement of particles (atoms, ions or molecules) from a region in which they are in higher concentration to regions of lower concentration. It continues until the concentration of substances is uniform throughout. Some major examples of diffusion in biology: Gas exchange at the alveoli — oxygen from air to blood, carbon dioxide from blood to air. Gas exchange for photosynthesis — carbon dioxide from air to leaf, oxygen from leaf to air. Gas exchange for respiration — oxygen from blood to tissue cells, carbon dioxide in opposite direction.

14. Cont ; Facilitated Diffusion If charged particles or large molecules are to move across the membrane, another process need to be found, as they are less soluble (or even insoluble) in lipid. They move through protein-lined pores. Channel proteins These are water-filled pores in the membrane which allows water-soluble molecules to easily pass through. Different channels allow different substances to pass through (the channels are selective ). Some channels are gated (they will only open when appropriately stimulated).

15. Cont ; Carrier proteins In this case, the substance actually combines with a protein and is carried from one side of the membrane to the other. This is the movement of specific molecules down a concentration gradient , passing through the membrane via a specific carrier protein. These proteins are specific for a particular substance. Substances move down the concentration gradient so no energy is required.

16. Cont ; L ike enzymes, each carrier has its own shape and only allows one molecule (or one group of closely related molecules) to pass through. Selection is by size; shape; charge. Common molecules entering / leaving cells this way include glucose and amino-acids.

17. Osmosis Osmosis is a special example of diffusion. It is the diffusion of water through a partially permeable membrane from a more dilute solution to a more concentrated solution – down the water potential gradient. Cell membranes are described as selectively permeable because not only do they allow the passage of water but also allow the passage of certain solutes.

18. Cont ; Some major examples of osmosis Absorption of water by plant roots. Re-absorption of water by the proximal and distal convoluted tubules of the nephron. Re-absorption of tissue fluid into the venule ends of the blood capillaries. Absorption of water by the alimentary canal — stomach, small intestine and the colon. Osmoregulation Osmoregulation is keeping the concentration of cell cytoplasm or blood at a suitable concentration. For example amoeba living in freshwater, uses a contractile vacuole to expel the excess water from its cytoplasm. In animals the kidneys maintain the normal blood concentration.

19. Cont ; Osmosis and Cells The movement of liquids in and out cells is dependent on the concentration of the solution surrounding it . There are 3 types of situations in which this could vary : Isotonic: Here the external solution concentration and the internal concentration of the organism are the same. Hypotonic: Here the external solution concentration is less than the concentration of the organism. In this case water will move into the organism. Hypertonic: Here the external solution concentration is greater than the concentration of the organism. In this case the water will move out of the organism.

20. Osmosis and Plant Cells

21. Water Potential This is a measure of the tendency of water molecules to move from one place to another. The symbol used for water potential is the Greek letter psi, ( Ψ ). Water always moves from a region of higher water potential to one of lower water potential, or down the concentration gradient. Solute potential and pressure potential The water potential of a cell is dependent upon the combination of its solute and pressure potentials. The water potential of pure water is zero and since adding solutes lowers water potential, they make the water potential less than zero, i.e. negative. The more solute, the more negative the water potential becomes.

22. Cont ; The amount that the solute molecules lower the water potential is called the solute potential. It always has a negative value and is given the symbol, Ψ s . Pressure also has a role to play in determining water potential. The greater the pressure inside a cell, the greater the tendency will be for water to leave it. This contribution to water potential is called the pressure potential. It always has a positive value because it increases water potential and is given the symbol Ψ p . Example : The water potential of pure water in an open container is zero because there is no solute and the pressure in the container is zero

23. Cont ; Adding solute lowers, the water potential. When a solution is enclosed by a rigid cell wall, the movement of water into the cell will exert pressure on the cell wall. This increase in pressure within the cell will raise the water potential. Below is the equation for water potential: Water Potential (ψ) = Pressure Potential ( ψ p ) + Solute Potential ( ψ s ) If the water potential surrounding an animal cell is higher than that of the cell, it will gain water, swell and burst. If the surrounding solution's water potential is lower than that of the cell, it will lose water and shrivel up. This is why it is so important to maintain constant water potential inside the bodies of animals.

24. Active Transport Active transport is the energy-demanding transfer of a substance across a cell membrane against its concentration gradient, i.e., from lower concentration to higher concentration . The energy for active transport comes from ATP generated by respiration (in mitochondria). The energy generated is then used to transport nutrients against the concentration gradient . Biological examples of active transport In plants the movement of nutrients from the soil into the root requires energy. In gardening, we aerate the soils to allow more oxygen reach the roots for aerobic respiration . Active transport is also experienced in the kidneys and villi of the small intestines. Re-absorption of glucose, amino acids and salts by the proximal convoluted tubule of the nephron in the kidney. Sodium / potassium pump in cell membranes (especially nerve cells).